Production and characterization of cellulases and hemicellulases from a consortium between Pleurotus ostreatus and Aspergillus niger cultured in agro-industrial wastes

The enzyme biosynthesis using agricultural wastes by solid state fermentation (SSF) and the study of their physicochemical properties are meaningful approaches to improve the biomass hydrolysis. Among them, β-glucosidases and β-xylosidases are key enzymes at the lignocellulose depolymerization, which act in the cleavage of oligosaccharides in monosaccharides. In this study, the production of hemicellulases and cellulases by Pleurotus ostreatus and Aspergillus niger monocultures or in consortium was investigated, using raw sugarcane bagasse (SB) and wheat bran (WB) as substrates. The highest enzymatic activities were observed in the crude extract produced by P. ostreatus PLO6 and A. niger SCBM4 consortium with 98.5, 62.9, 3.8, 12.4, 13.3 and 20.2 U/g for β-glucosidase (β-glu), β-xylosidase (Bxyl), filter paper cellulase (FPase), xylanase (Xyl), exoglucanase (Exgl) and endoglucanase (Engl), respectively. The pH and temperature effects on β-glu and β-xyl were characterized. Optimal activities were obtained at pH 4.0 and 45 °C for β-glu and 3.5 and 55 °C for β-xyl. Both enzymes were stable at acid pH and presented thermostability. The results indicated that the enzymatic cocktail demonstrated potential characteristics for future applications in saccharifications. The use of sugarcane bagasse and wheat bran for microbial growth contributed to aggregate value to these byproducts.

Isolation of Cellulose-Degrading Endophyte from Capsicum chinense and Determination of its Cellulolytic Potential

Knowledge in the field of bacterial endophytes associated with the plant Capsicum chinense is negligible. So in order to characterize the endophytic population in the targeted plant, different accessions of C. chinense plant were procured from different agro-climatic zones of India. Bacterial endophytes were isolated by using standard protocols. After isolation of the endophytes, a biochemical identification study was performed using the standard key. Secondary metabolites of these bacterial species were studied for their economic importance. One isolate of cellulose-degrading bacteria (CDB) was isolated from the roots of C. chinense. The cellulase activity of the endophyte, containing cellulose Congo Red agar. Finally, enzyme assays for the cellulase (endoglucanase) and filter paper cellulase or FPC assay was studied. The maximum clearing zone for the isolate was 50mm, and the hydrolytic capacity (HC) was found to be 5.96. The endoglucanase activity of 0.95 IU/mL and the filter paper Filter Paper Cellulase (FPCase) activity was found to be 0.25 IU/mL. The importance of the study is attributed to the fact that this is the first-ever study of the enzymatic activity of endophytic bacteria isolated from C. chinense collected from North-East India.

Isolation of Cellulose-Degrading Bacteria and Determination of Their Cellulolytic Potential

Eight isolates of cellulose-degrading bacteria (CDB) were isolated from four different invertebrates (termite, snail, caterpillar, and bookworm) by enriching the basal culture medium with filter paper as substrate for cellulose degradation. To indicate the cellulase activity of the organisms, diameter of clear zone around the colony and hydrolytic value on cellulose Congo Red agar media were measured. CDB 8 and CDB 10 exhibited the maximum zone of clearance around the colony with diameter of 45 and 50 mm and with the hydrolytic value of 9 and 9.8, respectively. The enzyme assays for two enzymes, filter paper cellulase (FPC), and cellulase (endoglucanase), were examined by methods recommended by the International Union of Pure and Applied Chemistry (IUPAC). The extracellular cellulase activities ranged from 0.012 to 0.196 IU/mL for FPC and 0.162 to 0.400 IU/mL for endoglucanase assay. All the cultures were also further tested for their capacity to degrade filter paper by gravimetric method. The maximum filter paper degradation percentage was estimated to be 65.7 for CDB 8. Selected bacterial isolates CDB 2, 7, 8, and 10 were co-cultured withSaccharomyces cerevisiaefor simultaneous saccharification and fermentation. Ethanol production was positively tested after five days of incubation with acidified potassium dichromate.

Effect of Steam Explosion Pretreatment and Microbial Fermentation on Degradation of Corn Straw

The effects of steam explosion (2.5 MPa, 200s) and Trichoderma koningii (T. koningii) fermentation on corn straw degradation were evaluated according to straw degradation and enzyme activity in the fermented products. The results showed that the steam explosion pre-treatment for corn straw could reduce the contents of cellose, hemicellulose and lignin by 8.47%, 50.45% and 36.65%, respectively (P<0.05). After the pretreated corn straw with steam explosion was fermented by T. koningii for 6 days, the contents of cellulose and hemicellulose in the fermented straw were decreased by 19.37% and 63.54%, compared with the original corn straw (P<0.05); decreased by 11.83% and 26.41%, compared with the exploded straw (P<0.05). The filter paper cellulase, CMCase and amylase protease protease protease;activities in the fermented products were 356.39,5 599.90 and 834.00 U/g, respectively. It is concluded that the corn straw pre-treated by steam explosion and followed by T. koningii fermentation for 6 days seems to be a new prospective method for corn straw degradation and application.

Development of mutants of Gliocladium virens tolerant to benomyl

Aqueous suspensions of conidia of Gliocladium virens strains Gl-3 and Gl-21 were exposed to both ultraviolet radiation and ethyl methanesulfonate. Two mutants of Gl-3 and three of Gl-21 were selected for tolerance to benomyl at 10 μg∙mL−1, as indicated by growth and conidial germination on benomyl-amended potato dextrose agar. The mutants differed considerably from their respective wild-type strains in appearance, growth habit, sporulation, carbon-source utilization, and enzyme activity profiles. Of 10 carbon sources tested, cellobiose, xylose, and xylan were the best for growth, galactose and glucose were intermediate, and arabinose, ribose, and rhamnose were poor sources of carbon. The wild-type strains and the mutants did not utilize cellulose as the sole carbon source for growth. Two benomyl-tolerant mutants of Gl-3 produced less cellulase (β-1,4-glucosidase, carboxymethylcellulase, filter-paper cellulase) than Gl-3. In contrast, mutants of Gl-21 produced more cellulase than the wild-type strain. Only Gl-3 provided control of blight on snapbean caused by Sclerotium rolfsii. Wild-type strain Gl-21 and all mutants from both strains were ineffective biocontrol agents. Key words: Gliocladium, benomyl tolerance, Sclerotium, rhizosphere competence.

Effect of Nutrients and Cellobiose Octaacetate on Cellulolytic Enzyme Productions by Streptomyces albolongus

The cellulolytic mesophilic isolate Streptomyces albolongus (A5) was used to determine the effect of nitrogen and carbon sources on the production of cellulolytic enzymes using cellobiose octaacetate (COA) as an inducer. The isolate was able to degrade various cellulosic carbon sources. However, the rate of degradation, production of extracellular protein, reducing sugar, saccharification and production of enzyme were enhanced when 0.6% COA was used as an inducer in addition to the main substrate. Among the nitrogen sources tested, beef extract showed maximum production of the enzyme (136.7 U/ml CMCase) in Winstead's medium. The enzyme production was further enhanced in the medium supplemented with 0.6% COA, which corresponded to 154.69 U/ml CMCase activity. Among the carbon sources, carboxymethylcellulose (CMC) was found to be the best carbon source and again supplementation of the medium with 0.6% COA enhances CMCase production. Other than CMCase activity, the organism also produced appreciable levels of filter paper cellulase (FPase), avicelase and â-glucosidase activities.Keywords: Streptomyces albolongus, Carboxymethylcellulose (CMC), Cellobiose octaacetate (COA), InductionDOI: http://dx.doi.org/10.3329/bjm.v24i1.1243 Bangladesh J Microbiol, Volume 24, Number 1, June 2007, pp 70-72